package com.acme.task1;

public class Calculator {
    public static void main(String[] args) {

        double operand1 = 0, operand2 = 0, result = 0;
        String errstr = null;

        //analyze number of arguments
        if (args.length != 3) {
            System.out.println("Wrong number of arguments.");
            return;
        }

        //get arguments
        try {
            operand1 = Double.parseDouble(args[0]);
            operand2 = Double.parseDouble(args[2]);
        } catch (NumberFormatException e) {
            System.out.println("Wrong operands.");
            return;
        }

        //analyze operation and make calculations
        switch (args[1].charAt(0)) {
        case '+':
            result = operand1 + operand2;
            break;
        case '-':
            result = operand1 - operand2;
            break;
        case '*':
            result = operand1 * operand2;
            break;
        case '/':
            if (operand2 != 0) {
                result = operand1 / operand2;
            } else {
                errstr = "Error: second operand is zero, "
                         + "division by zero.";
            }
            break;
        default:
            errstr = "Error: unknown operation.";
        }

        //print result at console like:
        if (errstr == null) {
            System.out.println(args[0] + " " + args[1] + " "
                               + args[2] + " = " + result);
        } else {
            System.out.println(errstr);
        }
    }
}
